Generally, in case of encoding source video stream into groups of pictures (GOPs) with a predetermined format and transmitting the GOPs over a communication channel under a target rate, a video processor may comprise an encoder to encode the source video stream, a controller to control an output rate of the encoder and a buffer to temporarily store the GOPs before being transmitted over the channel. The controller may control a target allocation (e.g., target bit number) for the encoder to encode a current frame based on a pre-determined target fullness for a buffer.